The production of polymeric film pouches, as well as the production of any other type of blank that provides for the thermal bonding of juxtaposed film flaps, is an extremely delicate industrial step.
A first problem that is observed is linked to the need to perform precise thermal bondings, which are both strong and capable of ensuring optimum tightness (for example tightness to liquids for any pouch being provided) regardless of the thickness of the polymeric film being processed.
Likewise, the need to perform the thermal bonding of superimposed flaps (for example layerings of multiple sheets superimposed at folds of the blank being provided, as occurs for example in the type of pouch known as “doypack”) increases the complexity of the thermal bonding operations, since it renders the thickness of the material on which the thermal bonding heads work uneven.
These requirements entail the use of thermal bonding assemblies that are capable of generating very high compression forces on the film.
The application of a very high pressure to the film by means of the thermal bonding heads requires the adoption of very rigid and consequently heavy thermal bonding assemblies.
Thermal bonding assemblies with such characteristics are preferably of the static type, differently from the film, which reaches them with a stepwise advancement motion.
A further requirement that can be observed universally in all machines for the packaging of pouches and/or of blanks made of polymeric film is that the thermal bonding assemblies, which are normally present in multiple quantities in order to perform different thermal bonding operations and/or to repeat thermal bonding operations that have already been performed, can be repositioned easily in order to adapt to the dimensional variations caused by pouches and/or by blanks of different shape and size.
These results are currently obtained by adopting thermal bonding assemblies that are supported by footings having a large mass (and consequent space occupation) in order to provide the support and the rigidity that are adequate for the intense forces generated during thermal bonding.
It is further preferable that the movement for relative approach of the thermal bonding heads toward the film to be subjected to thermal bonding be of the translational type instead of rotary, since this ensures a better distribution of the pressure on the area on which they will abut, regardless of the shape and dimensions of the latter.